This invention relates generally to wheel lock systems for use with wheelchairs and, more particularly, to lock systems that can lock a wheel of a wheelchair by motion of an operating lever in either one of two selectable directions.
Wheelchairs typically include wheel lock systems that can be used to lock one of the wheels of the wheelchair to hold the wheelchair in a fixed position. For more forceful and satisfying operation, a wheelchair wheel lock system should have an operating lever with positive engagement and good force multiplication. Most wheelchair wheel lock systems incorporate a mechanical linkage that effectively multiplies the force applied through the operating lever to provide secure wheel locking with a precise, positive operating feel, but many require physical abilities that some wheelchair occupants do not possess.
Due to particular arm strengths or disabilities, wheelchair occupants sometimes find they can only exert either a pushing motion or a pulling motion to engage the wheel lock system. Such occupants might also have a limited range of movement that allows them to move the operating lever over a restricted range in either direction. Conventional wheelchair wheel lock systems, however, often are designed for locking engagement in only one of the two directions of handle motion and cannot change the range of motion necessary for wheel locking. Thus, a wheelchair wheel lock system might be designed to be engaged by a pushing motion on the operating lever, while a wheelchair occupant might be limited to arm movement with strength in a pulling motion. To accommodate the widest population of wheelchair occupants, manufacturers must provide some wheelchairs with wheel lock systems configured for pull-to-lock operation and must provide others with push-to-lock operation. This causes increased production and inventory costs and can make it difficult for hospitals and supply agencies to ensure they have an adequate selection.
Wheelchair wheel lock systems have been proposed that allow either a pushing or pulling motion to engage the brake. Such dual-action systems provide increased flexibility and do not require increased inventory, but can be rather complicated and expensive to manufacture. If the cost of manufacturing the wheelchair wheel lock system is too high, it can be just as cost effective for the manufacturer to provide an inventory of wheelchairs with single-action lock systems separately capable of pushing motions and pulling motions. In addition, some wheel lock systems that provide the option of push-to-lock or pull-to-lock action may not provide a positive feel due to the complicated linkage, or can be somewhat difficult to switch between the two. One double action system is shown in Jinno et al. U.S. Pat. No. 4,749,064. Examples of typical single direction locking mechanisms are shown by Fought et al. U.S. Pat. No. 4,887,830 and Minnebraker et al. U.S. Pat. No. 4,570,756.
From the foregoing discussion, it should be apparent that there is a need for a wheelchair wheel lock system whose operating lever is selectable to operate in either a pushing or pulling motion and can accommodate wheelchair occupants with restricted strength in one direction of movement, while providing a mechanism that is simple and relatively inexpensive to manufacture. The present invention satisfies this need.